Mine sweeping control



March 26, 1946. w sCHAELCHLlN 2,397,209

' MINE swEEPING CONTROL Filed Feb. 27, 1942 2 Sheets-Sheet 2 ffy 4 O O O RNEY Q 8% ZW Patented Mar. 26, 1946 MINE SWEEPIN G CONTROL Walter Schaelchlin, Wilkinsburg, Pa., assignor to Westinghouse Electric Corporation, East Pitts- Y burg, Pa., a corporation of Pennsylvania Application February 27, 1942, Serial No. 432,651

12 Claims.

The practice of planting mines in navigable waters for the purpose of destroying merchant shipping is well known. Such mines are provided with detonating mechanism which is magnetically responsive to the magnetic eld set up by the steel hull of a passing ship. Accordingly, in those cases where it has been known or suspected that waters have been planted with mines, it has been customary to conduct mine sweeping operations to clear such waters of mines prior to the further passage of merchant shipping, the mine sweeping being done by traversing the suspected waters with a vessel towing an energized cable to provide a magnetic eld of intensity and direction equal to the distortion caused by the steel hull of a passing ship.

A recent development in the structure of magnetic mines has provided such mines with a delayed action whereby such mines would be operated only after being subjected to a predetermined number of separate magnetic impulses. Assuming that such a mine had been set to explode upon the seventh impulse, six vessels could pass over the mine safely before the mine would be responsive to a passing ship. To eiectively clear a field of such mines by sweeping operations, as heretofore practiced, several traverses of the mine held by a sweeping vessel would be required, a single traverse being no longer reliable. In addition to the increased time required for sweeping, an undesirable element of doubt has been raised since the actual number of sweeping traverses necessary to clear the field could not be determined.

One of the principal objects of this invention is to provide an apparatus which is eiective to activate a delayed action mine on a single traverse of the sweeping vessel. To this end, the sweeping cables carried by the mine sweeping vessel are provided with means by which such cables may be periodically energized to impart a plurality of separate magnetic impulses to the mines being swept. In this manner, mines in a given area being swept may be subjected to my desirable number of magnetic impulses to provide thesame effect as would be had by the passage of several ships. A mine sweeping vessel is thus enabled to accomplish in one traverse that which has heretofore required several traverses.

A further object of this invention is to provide mechanism which is automatically operable to interrupt and reestablish the field created by a mine sweeping cable.

A further object of this invention is to provide a timing control for a mine sweeping cable having means for energizing the same which is operable to cause the cable to be energized in a timed intermittent manner, and which is adjustable to vary the frequency of the current pulses flowing through the cable.

A further object of this invention is to provide a control for a mine sweeping cable which is operable to alternately reverse the flow of current through the cable to thereby intermittently reverse the magnetic field which is set up by such cable.

A further object of this invention is to provide a control which is operable to interrupt and reestablish the current flowing through a mine sweeping cable and which is further adjustable to vary the length of time during which current isflowing through the cable and to vary the length of time during which current is not flowing through the cable.

A further object of this invention is to provide a timing control for a mine sweeping cable which is variable over wide limits for adjusting the frequency of the current pulses flowing through the cable.

A further object of this invention is to provide an improved form of timing control comprising a constant torque motor vfor operating a rotatable timing member and a variable magnetic braking member which is adjustable to vary the speed of rotation of the timing member.

Further objects and advantages of the invention will become apparent during the following description taken in connection with the accompanying drawings, in which:

Figure 1 is a diagrammatic View illustrating the arrangement of mine sweeping cables with respect to a sweeping vessel;

Fig. 2 is a vertical sectional view of control apparatus constructed in accordance with the principles of my invention;

Fig. 8 is an exploded perspective View, parts thereof being shown in section, of the mechanism shown in Fig. 1;

Fig. 4 is a control circuit diagrammatically illustrating the manner in which the apparatus of my invention is made to control the flow of current through a mine sweeping cable;

Fig. 5 is a top plan view of a rotatable camming member showing its relation with respect to one of the control switches shown in Fig. 4;

Fig. 6 is a Vertical sectional View of a constant torque spring motor further shown in Figs. 2 and 3;

2,397,209 t i y i Fig. 'l is a graph illustrating the torque-deflection characteristics oi the torque motor shown in Fig. 6;

Fig. 8 is a top plan View of a p-art of the control casing shown in the arrangement oi a brake lever with respect thereto; and

Fig. 9 is a side elevational view oi the brake lever and associated parts shown in Fig. 8.

In Fig. l, the numeral I designates a sweepingy vessel for sweeping cables 2 and 3 which are respectively provided with electrodes 4 and 5. As

best shown in Fig. 4, the terminals of the cables 2 and 3 are connected to the armature of a directcurrent generator 6 having an exciting field l. In practice, the cables 2 and 3 are arranged in such manner that the distance between the electrodes 4 and 5 is approximately 2000 feet. I'he generator S supplies the cables with a. current of from about 2000 amperes to about 300D amperes,

and in one D314; f the circuit Such. cllrren'b Will. :How through. the water 'be-twee the electrodes 4 the intensity and drectin of the eld caused by a steel 11u11 of a. passing ship.

If the generator 6 is operated in such manner th-at the current flows continuously in the same direction between the-electrodes 4 and 5, the effect on a mine subjected to the action of the magnetic eld set up by such current will be similar to the passage of a single ship. If such mine is provided with a delayed action mechanism, it will be necessary to sweep the field several times in order to make Vthe mine responsive to the magnetic eld set up. The control of this inventionY is adapted to interrupt and reestablish the current through the cables 2 and 3 in order that the magnetic field may be applied a plurality of times to a mine within the rangeof the cable 2 and 3. In this manner, an effect similar to the passage of several ships is produced. Since the sweeping mechanism is installed on ships of various sizes and speeds, it is necessary that the frequency of the current pulses flowing in the cables 2 and 3 be variable over wide limits in order that a given area of a mine eld being traversed will be subjected toa given number of magnetic impulses notwithstanding the speed of the sweeping vessel. As will be apparent, the timing control of this invention is adjustable over Wide limits to compensate for the speed of the sweeping vessel. The control of thissinvention is also adapted to reverse the ow of current through the cables 2 and 3 in order to reverse the polarity of the magnetic eld, a feature which has been found desirable in mine sweeping operations.

Referring now to Fig. 4, the field 1 is energized from a direct-current source through either of the control switches 8 or 9. The control switches 8 and 9 reverse the connections on the eld 'I to the direct-current source and are thus operable to reverse the polarity of the generator -6 and the direction of current ow through the cables 2 and 3. vThe switches 8 and 9 are respectively operated by solenoids Ill and II, which are operated by small switches I2 and I2 under the control of means, or device, I3.

As best shown in Figs. 3 and 5, each of 'the control switches comprises upper and lower resilient conducting members I4 and I4' and I5 and l5', carried by insulating supports I6 and I6'. Then conducting members are' provided with contacts Il and Il' which are engageable tocomthe solenoid sociated switch 9 will drop open to deenergize plete the operating circuit for the solenods I0 and II respectively. The rotatable control means I3 comprises like upper and lower cams I8 and I9 which are angularly adjustable relative 24 provided the finger 2 :is a1: such. time 1 engagement with tha portxon of une cam ISV ying e out'of engagement and thus interrupt circuit to one of the'operating solenolds, as solenoid II. Such circuit will not again be reestablished until subsequent rotation of the means I3 to again hold the position shown in Fig. 5, permitting the nger 2l' to move inwardly to close the contacts Il.

During that time in which the fingers 2l' and 22 are in engagement with any portion of the cams between the radial lines 23 and 24, the operating solenoid I I will be energized and the eld I will be energized and current will flow through the cables 2 and 3. VAs the fingers 2| and 22' move'out of engagement with those portions of the cams lying between the lines 23 and 24,

II` will Ybe energized and its asthe eld 'I and thus stop the flow of current through the cables 2 and 3. The device I3 is thus operative to cause current to flow through f the cables Zand 3 in an intermittent manner.

By angularly shifting the cams I8 and I9 relative to each other to increase the angle between the lines 23 and 24, the portion of the cycle during which current is caused to flow is increased and the portion of the cycle during which no current `flows is correspondinglyv decreased. The construction of the cams I8 and I9 is such that adjustments may be made to cause closure of the contacts I'I and consequent flow of'current in the cables 2 and 3 during from about 5% Vto about of the time of any given Cycle. In this manner, the device I3 is adjustable to vary the length of time during which current is flowing through the cables and to vary the length of time during which current is not flowing through the cables. Indicia may be markedfon the surface 25 of the cam I9 for cooperation with the edge 26 of the cam I 8 to indicatethe portion of the cycle during which current will be caused to flow through the cables2 and 3.

In the arrangement shown in Fig. 4, rotation of the device I3 is effective to close first the switch I24to energize the solenoid II and thereby close the switch 9 to energize the eld 1. Continued rotation of the device I3 opens the switch I2 and interrupts the iiow of current through the field 'I and thus stops the flow of current through the cables 2 and 3. Further rotation of the device I3 closes switch I2 to energize solenoid Ill and thereby close the switch 6 to reverse the excitation of the eld 1 and thus reverse the now of current in the cables 2 and 3. Continued rotation of the device I3 is 'thus operative to alternately reverse the direction of current flow through the cables 2 and 3 and to provide time intervals between the current reversals during which no current flows through the cables 2 and 3.

Since two or more ships are frequently operated side by side in sweeping operations and the switches 3 and 8 operate to reverse the flow of current in the field 1, lights 21 and 28 are provided to indicate which of the switches 8 and 9 have been operated. The lights 21 and 28 are operated from an alternating-current source and their circuits are controlled by contacts 29 and 36, respectively, carried by the switches 8 and 8. Upon operation of one of the switches 8 or 9, the corresponding light 21 or 28 will be operated to indicate not only which switch has been operated, but also the time during which the field 1 is energized. By this arrangement, it is possible to synchronize the operation of diierent units mounted on different ships in order that the polarity of the fields established by the sweeping cables will be the same and will not buck each other. It is also possible through the lights 21 and 28, to adjust the cams i8 and I9 so that the duration of current flow in the different cables on diiferent ships will be the same.

Since the delayed action of some mines may require as many as 15 impulses before the mine will be responsive to a magnetic field, it is necessary that the speed of rotation of the timing member I3, and thereby the frequency of magnetic impulses developed by the sweeping cables, be adjustable according to the speed of the ship on which the control is mounted. It has been determined that the frequency of magnetic impulses should vary between and 140 seconds per cycle in order that the control will be adjustable to compensate for the various speeds of sweeping. The driving mechanism of this invention for the device I3 answers these requirements and is best shown in Figs. 2, 3 and 6.

Referring to Figs. 2 and 3, the cams I8 and I9 comprising the rotatable device I3 are adjustably mounted on a shaft 3l which has a driving pinion 32 keyed thereto. The pinion 32 is driven by a gear 33 mounted on a shaft 34 which, in turn, is driven by a pinion 35 meshing with a driving gear 36 keyed `to a driving shaft 31. The driving shaft 31 is driven by a constant torque motor of novel design indicated as a whole by the numeral 38.

The constant torque motor 38 comprises a sleeve member 39, best shown in Fig. 6, which is keyed to the shaft 31, the shaft 31 being rotatably mounted in bearing blocks 48 carried by the casing 4I. A pair of lever arms 42 project outwardly from the sleeve 38 and have their opposite ends tied together by connecting members 43. A gear cage 44 comprising a pair of spaced gears 45 tied together by connecting members 46 is mounted by bearings 41 for rotation about the shaft 31. Torque is applied to the shaft 31 through the lever arms 42 by a pair of springs 48. Each of the springs 48 has one of its ends anchored to one of the gear cage connecting members 46 and its other end to one of the lever arm connecting members 43. The springs 48 are placed under tension which is effective to transmit torque to the lever arms 42. The torque applied to the lever arms 42 is a function of the tension in the springs 48 and the angular displacement of the lever arms 42 relative to the cage 44. Fig. '1

graphically illustrates the torque developed by the lever arms 42 against the angular displacement of the cage 44 relative to the lever arms 42. It will be noted that the torque-angular displacement curve is substantially hat and a. maximum between the vertical lines 49 and 50. The angular displacement of the lever arms 42 represented by the distance between the lines 4S and 58 represents about a 10 travel of the arms 42. The torque motor 44 is operated in such manner that the angular displacement of the lever arms 42 relative to the cage 44 is not more than 5 and is maintained between the lines 48 and 58 so that the tension of the springs 48 and torque transmitted to the arms 42 will be substantially constant. Y

To maintain the tension of the springs 48 substantially constant, a suitable motor 5I is mounted in a housing 52 carried by the casing 4I and is operated to drive a shaft 53 carrying a pinion 54 meshing with the gears 45 of the gear cage 44 after angular displacement of the lever arms 42 relative to the gear cage 44. This action is had through a follow-up arrangement of contacts 55 and 56 respectively carried by one of the lever arms 42 and one of the gears 45, the contacts 55 and 56 controlling the circuit to the motor 5I The contacts 55 and 56 are electrically connected to slip rings 51 and 58 which are tied in with the control circuit for the motor 5I through brushes 59 and 60. The control circuit for the motor 5l, asbest shown in Fig. 4, is energized from the direct-current bus bars upon movement of the contactors 55 and 56 into engagement with each other. Upon movement of the lever arms 42 by the tension of the springs 48 the contact 55 carried by one of the lever arms 42 will move into engagement with the contact 56 carried by one of the gears 45, and the motor 5I will then be energized to rotate the pinion 54. Rotation of the pinion 54 will impart movement to the gears 55 to displace the cage 44 approximately 5 with respect to the lever arms 42. Such movement of the cage 44 will move the contact 56 out of engagement with the contact 55 and interrupt the circuit to the motor 5I, thus stopping the motor until further movement of the lever arms 42 operates to move the contact 55 into engagement with the contact 56.

The various shafts carrying the gear units constituting a gear train intermediate the motor 38 and rotatable driving shaft 3| are carried by suitable bearings selected so as to introduce as little friction as possible. Since the motor 38 is a constant torque motor, braking means is provided to control the speed of rotation of the shaft 3|. The braking means is indicated as a whole by the numeral 6I and comprises a vertical support 62 secured to the casing 4I and having a pair of arms 63 and 64 projecting outwardly therefrom. The upper arm 63 has a stationary support 65 depending downwardly therefrom on which a magnet carrying member 66 is slidably mounted. The member 66 is provided with a plurality of U-shaped permanent magnets 61 and an annular ring 68 of magnetic material spaced from the pole faces of the magnets 61. The space 69 intermediate the magnet 61 and the ring 68 constitutes an air gap for the magnetic circuit of the magnets 61. A pinion 18 is mounted on a shaft 1I having its ends rotatably mounted in bearings formed in the lower end of the depending member 65 and on the upper surface of the inwardly projecting bracket member 64. An aluminum disc 12 is secured to the pinion a, part of the gear train 14 for driving the disc 12. This gear train is designed to impart a high speed of rotation to the disc 12, and more particularly, is designed to rotate the disc 12v at a ratio of 500:1 with respect to the driving shaft 31.

The magnets 61 exert a braking force upon rotation of the flange 13 which is increased proportionately to the amount of the flange 'I3 extending into the space or air gap 69. The speed of rotation of the disc 'I2 varies directly with the position of the member 66 and a curve plotting the speed of rotation of the disc 12 against 'the vertical displacement of the magnet carrying member 66 will be found to be a straight line. In order to'adjust the vertical position of the member 66 with respect to the disc 12 an adjusting member 16 is rotatably mounted in the bracket member 63 and is provided with a threaded end 11 having threaded engagement with the plate 56. Upon rotation of the member 16 by the knurled knob 18, the magnet 68 will be moved up or down to vary the braking effect on the flange 'I3 and thereby the speed of rotation of the disc 'Il and the driving shaft 3l for the rotatable control member I3. The knob 'I8 is a Calibrating knob and is provided with two dials I9 and 8i! marked in degrees. Indicating members 8| and 82 are carried by the casing III to indicate the relative positions of the dials 19 and 80. The dial 80 is driven from a knob 18 through a gear train 83 which gives a 3,0:1 ratio. The Vernier dial 19 attached to the knob 18 is marked 12 for one revolution and thelarge dial B is marked 360 for one revolution. By suitable operation of the adjusting knob 18, the speed of rotation of the control member I3, andY thereby the frequency of current pulses imparted to the sweeping cables 2 and 3, may be 'adjustedv to compensate for the speed at which the sweeping operation is to take place. y

The driving shaft 3l has an annular braking member 84 keyed thereto for engagement by a brake shoe 85 carried by a shaft 8B. The shoe 85 may be moved into engagement with the brake 84 by a bracket member 81 keyed to the shaft 86. An operating member 88 is provided on the top of the casing Ill as best shown in Figs. 8 and 9, for imparting movement to the brake shoe 85. Upon movement of the member 88 lto the left, as viewed in Fig. 8, the brake `shoe 85 will be moved into engagement with rthe brake SII to effect a momentary slowingrdown of the control. This feature is desirable when operating controls on` on and time olf period of the current flowing in the sweeping cables. Thereafter the'vernier dial 18 is operated to adjust the Vertical positlon'of the magnet carrying member 6G and thereby the braking effect on thegear train 14 to secure the proper speed of rotation of the control member I3. This latter adjustment controls the frequency of the current pulses owing in they sweeping cables. In the event that two or more ships are to be operated side by side, it is possible to synchronize the controls mounted on the different ships by watching the lights 21 and 28, which preferably are colored differently, and adjusting the cams I8 and I9 and the Vernier control 18 until such lights flash synchronously. In the event that it is necessary to stop one of the controls in order to adjust the angular positionl of the cams I8 and I9 to vary the length of the time on period of current flow, the brake operating member 88 enables such control to be synchronized with other controls with a minimum of effort after such an adjustment. After making the adjustment of the angular position of the cams I8 and I9, the control is then placed in operation. If, after adjustment, such control is out of phase with controls on other ships, it is merely necessary to operate the braking control 88 to effect a momentary slowing down of the control until it is placed in proper phase relationship with the other controls.

From the foregoing it will be apparent that the apparatus of this invention p rovides an effective means for controlling the ow of current throughV a mine sweeping cable. The rotatable control member I3 together with the switches I2 and I2' provides means for causing the current to' flow through the sweeping cables intermittently in timed pulses of adjustable duration. As pointed out above, adjusting the angular positions of the cams I8 and I9 is effective to vary the time on and time off periods of the current pulses. By the use of the two switches I2 and I2 and their associated circuit controls, the current flow through the sweeping cable is alternately reversed. In the event that reversal of current ow in the sweeping cable is not desired, it is merely necessary to eliminate one of the switches I2 or l2 magnetic braking means 5I, and the intermediate gear train 64 provides an effective means for varying the speed of rotation of the control I3 and thereby the frequency of the current pulses supplied to the sweeping cable.

Since certain changes may be made in the above `described construction and different embodiments of the invention may be made without departing from the scope thereof, it is intended that all um matter contained inthe above description or vshown in the accompanying drawings shall be interpreted as illustrative -and not in a limiting sense. Y

I claim as my invention: l. In apparatus for sweeping mines responsiv to a plurality of Vconsecutively applied impulses, thecombination with transmitting means operative to produce a mine affecting condition, of control means for periodically rendering said trans- Y mitting means operative to cause the consecutive transmission of a plurality of intermittent mine affecting impulses.

2. In apparatus for sweeping mines responsive to a pluralityof consecutivelyY applied impulses, l the Ycombination with transmitting means operative to produce a mine affecting condition, of control means actuable to render said transmitting means operative, and timing means for periodically actuating said control means to produce a succession of mine affecting impulses.

3. In apparatus for sweeping mines responsive to a plurality of consecutively applied magnetic impulses, the combination, with transmitting means operative to create a magnetic field to produce a mine affecting magnetic condition, of control means for periodically rendering said transmitting means operative to cause the consecutive transmission of a plurality of intermittent mine affecting impulses.

4. In apparatus for sweeping mines responsive to a plurality of consecutively applied magnetic impulses, the combination with transmitting means operative to create a magnetic eld to produce a mine affecting magnetic condition, of control means actuable to render said transmitting means operative, and timing means for periodically actuating said control means to produce a succession of mine aiectlng magnetic impulses.

5. In a control system for a mine sweeping cable, a cable, disposed in the sea, of the type for carrying an electric current to produce an electric condition in the sea to detonate mines, control means operable to cause current to ow through said cable in one direction, a second control means operable to cause current to flow through said cable in a reverse direction, and means for alternately operating one and then the other of said control means in timed relation.

6. In a control system for a minesweeping cable, a cable, disposed in the sea, of the type for carrying an electric current to produce an electric condition in the sea to detonate mines, control means operable to cause current to flow through said cable in one direction, a second control means operable to cause current to flow through said cable in a reverse direction, means for selectively operating said control means, and separate means associated with each of said control means for indicating the control means operated.

'7. In a control for a mine sweeping cable, a

cable, disposed in the sea, of the type for carry ing an electric current to produce an electric condition in the sea to detonate mines, electric current generating means for energizing the cable, a switch for controlling the energization of said cable, and a timing device periodically operating said switch to eiect intermittent energization of said cable.

8. In a control for a mine sweeping cable, a cable, disposed in the sea, of the type for carrying an electric current to produce an electric condition for aiecting mines placed in the sea, electric current generating means for energizing the cable, a pair of switches for controlling the time of energization and time of deenergization of said cable, and a timing device for operating one and then the other of said switches in consecutive fashion to intermittently energize said cable for predetermined periods.

9. In a control for a mine sweeping cable, a cable, disposed in the sea, of the type for carrying an electric current to produce an electric condition for aiecting mines placed in the sea, electric current generating means for energizing the cable, a switch controlling the energization of said cable, a rotatable member for operating said switch, and timing means for driving said member comprising a constant torque motor, a gear train connecting said member to said motor, and retarding means controlling the speed of rotation of said member.

10. In a control for a mine sweeping cable, a cable, disposed in the sea, of the type for carrying an electric current to produce an electric condition for affecting mines placed in the sea, electric current generating means for energizing the cable, a switch controlling the energization of said cable, a rotatable member for operating said switch, and timing means for driving said member comprising a constant torque motor, a gear train connecting said member to said motor, 'and retarding means controlling the speed of rotation of said member, comprising a stator providing a magnetic field, and a rotor rotatable in said magnetic field and driven by said gear train, said field exerting a braking effect on said rotor.

11. The combination as claimed in claim l0, together with means to adjust the position of said stator with respect to said rotor to thereby vary the braking effect of its field on said rotor and the speed of rotation of said member.

12. The combination as claimed in claim 9, wherein said train is provided with a driving shaft and a driving gear keyed thereto, and said torque motor comprises a driving lever arm keyed to said shaft, a support rotatable independently of said shaft, a spring connected to said lever arm and said support, and means for rotating said support to maintain a substantially constant tension in said spring.

WALTER SCHAELCHLIN. 

